1. Field of the Invention
Embodiments of the present invention relate generally to semiconductor wafer processing apparatuses and associated methods. More particularly, embodiments of the invention relate to semiconductor production apparatuses capable of processing batches of wafers including variable numbers of wafer lots.
A claim of priority is made to Korean Patent Application No. 10-2005-0074253, filed Aug. 12, 2005, the disclosure of which is hereby incorporated by reference in its entirety.
2. Discussion of Related Art
Semiconductor devices are manufactured by constructing layers of insulating and conducting materials on wafers of silicon to form intricate circuit patterns giving the devices their functionality. The manufacturing processes used to form the layers typically include hundreds of different processing steps performed under a variety of different processing conditions. These steps include, for example, cleaning, diffusion, photoresist coating, exposure, developing, etching, ion implantation, and so on. The processing steps generally require intricate timing and process flow specifications including interrelationships between the different steps.
A “recipe” is a codified description that provides some or all of the ingredients, process steps, and machine and equipment operations involved in manufacturing a particular semiconductor device. Due to the large number of processing steps and the interrelatedness of processing inputs involved in most recipes, it is often difficult to specify optimal ranges for all of the inputs to a recipe. Moreover, there may be variation in the way that different pieces of processing equipment perform different processing steps according to a particular recipe. Accordingly, empirical evaluations of a recipe's performance with respect to a particular piece of processing equipment are often carried out after performing selected processing steps so that adjustments to the recipe can be made to improve its performance in subsequent wafer processing.
For example, after a recipe is carried out to produce a semiconductor device, the device may be inspected for defects. If the inspection indicates that the recipe produces defective devices, the processing equipment used to carry out the recipe will typically halt execution and generate a warning so that an engineer can evaluate the cause of the defects and attempt to resolve them by making adjustments to the recipe or the processing equipment. If the engineer is able to resolve the defects through adjusting the recipe or the processing equipment, then the processing equipment is allowed to resume performing its functions.
The recipes used with a set of semiconductor processing equipment are typically stored in a database connected to the equipment. For example, most modern semiconductor processing equipment comprises a host computer adapted to store the recipes.
Semiconductor manufacturing processes are often carried out on many wafers at a time. A group of semiconductor wafers that are processed together is commonly referred to as a “wafer lot.” A typical wafer lot includes between 20 and 25 wafers. In addition, some semiconductor manufacturing processes are carried out on batches of wafers, where a batch includes multiple lots of wafers. A typical batch of wafers includes between 1 and 6 wafer lots.
When many wafers are processed at the same time, one of the wafers may be designated as,a monitoring wafer. The monitoring wafer may be inspected and the inspection of the monitoring wafer may be used to infer the quality of processes concurrently performed on other wafers.
Semiconductor processing equipment used to process multiple batches of wafers at a time will be referred to as “batch-type semiconductor processing equipment” in this written description. A single unit of batch-type semiconductor processing equipment can often be used to process variable-sized batches of wafers, or in other words, batches of wafers having a variable number of lots.
Most batch-type semiconductor processing equipment operates according to a table that specifies the number of lots processed and whether or not a monitoring wafer is used to judge the quality of the processed wafers. In the absence of such a table, the wafers may be inappropriately processed because the process settings for processing one number of lots (e.g., 4) is different from the process settings used to process a different number of lots (e.g., 6).